Known road pavers include a material bunker for receiving paving material at the front of the road paver with respect to the paving direction of travel. During paving, the paving material is fed via suitable conveying equipment of the road paver from the material bunker to a paving screed pulled behind the paver for compacting the paving material. Paving screeds are known to be provided with lateral extension parts on both sides. The paving width covered by the paving screed can be adjusted to the geometry of the road to be paved by laterally extending or retracting the extension parts perpendicular to the direction of travel of the road paver. The paving working width of the screed is usually controlled manually by a paving screed operator on the left or right-hand side of the paving screed by extending or retracting the extension part for each side.
The paver rotates around a vertical yaw axis (yaw motion) when paving a curve with the paver during a paving run. In road pavers with a crawler track, the yaw axis is located approximately in the centre of gravity of the road paver. In road pavers with a wheeled track, the yaw axis is located in between the unsteered wheels of the rear axle. That means the yaw axis is located in front of the paving screed with respect to the paving direction of travel in both cases. Since the paving screed and its extension parts are located behind the paving screed's yaw axis with respect to the paving direction of travel, they both pivot together when driving on a curve. In particular, a lateral outermost rear point of an extension part of the paving screed on an inner side of the curve swivels from an edge of the target road way on an inner side of the curve towards the road edge on the outer side of the curve. This leads to a step in the road edge on the inside of the curve. In practice, this step is manually controlled by the paver operator by adjusting (extending) a lateral extension position of the paving screed's extension part on the inside of the curve to compensate for any offset of the paving screed. This requires the attention of the operator, who must also perform other tasks, such as instructing the driver, especially when the road paver is driving around a curve. Since the operator can only control the step in the road edge manually when the offset of the paving screen has already occurred, even an experienced paver operator will always have an offset and thus a defect in the road. On the outside of the curve, too, there is an offset of the paving screed, here particularly in an outward direction with respect to the road to be paved. As a rule, it is not possible for the operator to quickly and accurately adjust the extension positions of the extension parts of the paving screed on both sides.
A road paver is known from the EP 3 106 562 A1, which is equipped with a sensor that detects a line on the ground along which the road surface is to be paved. Based on a sensor signal, a distance between the line and a side plate of the paving screed is determined. This distance is used to adjust an extension position of the side plate relative to the line. The detected line may be an edge of a section of a road to be widened or a tensioned guide wire, for example. The disadvantage of this system is that it must be ensured before paving begins that the reference line followed by the side plate of the paving screed corresponds to the desired course of paving or that a guide wire has to be mounted with great effort.
EP 0 620 319 B1 also discloses the adjustment of an extension position of a lateral extension part of a paving screed based on a measured distance to a reference line at ground level. In this system, two sensors spaced apart along the paver's direction of travel are provided on the paving screed's extension part, each of which detects the distance to the reference line. Depending on whether a narrowing, a widening area or an area of constant width of the road is being paved, either the distance to the reference line measured by the rear sensor or the front sensor is used to set the extension position of the extension part of the paving screed. This is done to better adapt the extension unit's extension position to the course of the road. This system also requires the presence of a clearly detectable reference line following the desired course of paving.